Not to sound like a smartass, but I've always wondered why would you want it? You're taking a great handling bike and now making it into a crummy handling one. Is it just the look, or am I missing something I've been taught about suspension geometry?
Trac Dynamics makes very nice swing arms. I have one for my Z1. I think they are the best thing going. Do a google search for "trac dynamics ZX11". That will get you in the ball park. When I just searched "trac dynamics" I came up with the TD site but it was all busa stuff. When I searched "trac dynamics ZX11" I was able to find their ninja stuff. Weird. Anyway, they are very nice but you better be ready to spend some money. Base price $1000 plus more for options like air tank in the arm for shifter and a bracket for nitrous bottle, plus more if you want something other than the standard finish. Check it out.